As promised, Asimov's 300th book comes out just before his 65th birthday, in January. Like Opus 1O0 (1969) and Opus 200 (1979), this too is a collection: selected pieces from the preceding 99 works. Asimov coyly admits to some number-fudging: the count includes co-authorings and Asimov anthologies. (No less than 54 anthologies help make up the 300 works.) But what's to quibble? It takes time and talent to edit anthologies; besides, everybody expects "prolificity" of him. So this is a feast for fans--and also a varied sampling for newcomers; more pleasing in many ways than the encyclopedic Asimov's New Guide to Science (p. 834). That volume obligated Asimov to cover all fields; here he can pick and choose from favorite things. In recent years, that means the usual sciences--astronomy, physics, chemistry, biology--as well as the social sciences, history, the Bible, science fiction, and more. There are gems: on the deadness of the moon; on icebergs; on matter/antimatter collisions. There is an amusing sample of armchair sleuthing; a quite sensitive handling of "humaniform" robots (from the latest robot volume); even an essay never before published--on immortality, and why Asimov is against it. (Perhaps, he speculates, the editors didn't like the point of view.) These last years Asimov has joined the battle against creation science, so there are good pieces on evolution, along with the tedious annotations of Genesis. There are silly limericks and not-so-funny humor bits to contend with too. With official autobiography, and also running commentary--noting background and mood, saluting or mourning friends: the ruminative as well as the energetic Asimov, already on the road to Opus 400.